Thin film transistor array substrate, method for manufacturing the same and system for inspecting the substrate

ABSTRACT

Disclosed is a thin film transistor substrate and a system for inspecting the same. The thin film transistor substrate comprises gate wiring formed on an insulation substrate and including gate lines, and gate electrodes and gate pads connected to the gate lines; a gate insulation layer covering the gate wiring; a semiconductor layer formed over the gate insulation layer; data wiring formed over the gate insulation layer and including data pads; a protection layer covering the data wiring; auxiliary pads connected to the data pads through contact holes formed in the protection layer; and a pad auxiliary layer formed protruding a predetermined height under the data pads. The inspection system for determining whether a thin film transistor substrate is defective, in which the thin film transistor substrate comprises gate wiring including gate lines, gate electrodes and gate pads, and data wiring including source electrodes and drain electrodes, includes a probe pin for contacting the gate pads or data pads and transmitting a corresponding signal, wherein a contact tip at a distal end of the probe pin for contacting the gate pads or the data pads is rounded, and a radius of the rounded contact tip is 2 μm or less, or the rounded contact tip is coated with gold (Au).

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a Continuation Application of Applicant's U.S.patent application Ser. No. 10/602,052 filed on Jun. 24, 2003 now U.S.Pat. No. 6,827,121, which is a Divisional Application of U.S. patentapplication Ser. No. 09/970,785 filed Oct. 5, 2001, now issued as U. S.Pat. No. 6,590,226, which claims priority to and the benefit of KoreanPatent Application No. 2000-65860, filed on Nov. 7, 2000, which are allhereby incorporated by reference for all purposes as if fully set forthherein.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a thin film transistor array substrate.More particularly, the present invention relates to a thin filmtransistor array substrate, a method for manufacturing the same and asystem for inspecting the substrate.

(b) Description of the Related Art

Liquid crystal displays are at present the most commonly used flat paneldisplay. The liquid crystal display (LCD) is structured having liquidcrystal material injected between two substrates. Voltages of differentpotentials are applied to electrodes of the substrates to form electricfields such that the alignment of liquid crystal molecules of the liquidcrystal material is varied. Accordingly, the transmittance of incidentlight is controlled to enable the display of images.

Formed on one of the substrates is wiring, which transmits image signalsand scanning signals. The wiring defines pixels in a matrix arrangement,and each pixel is electrically connected to the wiring. Formed on thesame substrate as the wiring are thin film transistors (TFTs) fordiscontinuing the transmittance of the image signals, and pixelelectrodes for transmitting the image signals. This substrate isreferred to as a TFT substrate.

Pads are connected to ends of the wiring. The pads are used as a meansto transmit the scanning signals and image signals to the wiring from anexternal drive circuit. To prevent damage to the pads, it is preferableto cover the pads with auxiliary pads made of a conducting material inanother layer.

However, a space between the pads decreases as the resolution of the LCDincreases. Thus, contact defect of a probe pin used in inspecting theliquid crystal panel increases contact resistance of the pads. This isparticularly true when IZO (indium zinc oxide), which has a high surfacecontact resistance, is used for the auxiliary pads, making it unable toinspect the liquid crystal panel.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the aboveproblems.

It is an object of the present invention to provide a thin filmtransistor array substrate, a method for manufacturing the same, and asystem for inspecting the substrate that lowers a contact resistancewith a probe pin.

To achieve the above object, the present invention provides a thin filmtransistor substrate comprising gate wiring formed on an insulationsubstrate and including gate lines, and gate electrodes and gate padsconnected to the gate lines; a gate insulation layer covering the gatewiring; a semiconductor layer formed over the gate insulation layer;data wiring formed over the gate insulation layer and including datapads; a protection layer covering the data wiring; auxiliary padsconnected to the data pads through contact holes formed in theprotection layer; and a pad auxiliary layer formed protruding apredetermined height under the data pads.

According to a feature of the present invention, the pad auxiliary layeris formed on a same layer as the semiconductor layer.

According to another feature of the present invention, the pad auxiliarylayer is formed on a same layer as the gate wiring.

According to yet another feature of the present invention, the datawiring further includes data lines, source electrodes connected to thedata lines, and drain electrodes provided opposing the source electrodeswith respect to the gate electrodes.

According to still yet another feature of the present invention, thesubstrate further comprises pixel electrodes formed on a same layer asthe auxiliary pads and connected to the drain electrodes.

According to still yet another feature of the present invention, thesubstrate further comprises an ohmic contact layer formed between thesemiconductor layer and the data wiring, the ohmic contact layer beingdoped with impurities at a high concentration.

According to still yet another feature of the present invention, theohmic contact layer is formed in the same shape as the data wiring.

According to still yet another feature of the present invention, thesemiconductor layer, except for a channel formed between the sourceelectrodes and the drain electrodes, is formed in the same shape as thedata wiring.

According to still yet another feature of the present invention, the padauxiliary layer is made of an aluminum group conducting material, theauxiliary pads are made of IZO, and the pad auxiliary layer and theauxiliary pads are interconnected via the contact holes of the datapads.

In another aspect, the present invention provides a thin film transistorcomprising gate wiring formed on an insulation substrate and includinggate lines, and gate electrodes and gate pads connected to the gatelines; a gate insulation layer covering the gate wiring; a semiconductorlayer formed over the gate insulation layer; data wiring formed over thegate insulation layer and including data lines, source electrodesconnected to the data lines, drain electrodes provided opposing thesource electrodes with respect to the gate electrodes, and data padsconnected to the data lines; a protection layer covering the datawiring; and pixel electrodes connected to the drain electrodes throughcontact holes formed on the protection layer, wherein the protectionlayer or the gate insulation layer is removed at pad portions where thedata pads are formed such that at least the data pads are fully exposed.

According to a feature of the present invention, the thin filmtransistor further comprises auxiliary pads formed on a same layer asthe pixel electrodes and covering the data pads.

The inspection system for determining whether a thin film transistorsubstrate is defective, in which the thin film transistor substratecomprises gate wiring including gate lines, gate electrodes and gatepads, and data wiring including source electrodes and drain electrodes,includes a probe pin for contacting the gate pads or data pads andtransmitting a corresponding signal, wherein a contact tip at a distalend of the probe pin for contacting the gate pads or the data pads isrounded, and a radius of the rounded contact tip is 2 μm or less, or therounded contact tip is coated with gold (Au).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate an embodiment of the invention,and, together with the description, serve to explain the principles ofthe invention:

FIG. 1 is a schematic view for describing a step in inspecting a thinfilm transistor array substrate for a liquid crystal display accordingto a preferred embodiment of the present invention;

FIG. 2 is a schematic view of a thin film transistor substrate for aliquid crystal display according to a first preferred embodiment of thepresent invention;

FIG. 3 is a sectional view taken along line III–III′ of FIG. 2;

FIG. 4 is a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a second preferredembodiment of the present invention;

FIG. 5 is a sectional view taken along line V–V′ of FIG. 4;

FIG. 6 is a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a third preferredembodiment of the present invention;

FIG. 7 is a sectional view taken along line VII–VII′ of FIG. 6;

FIGS. 8A, 9A, 10A and 11A are schematic views sequentially illustratingan intermediate process in the manufacturing of a thin film transistorsubstrate for a liquid crystal display according to a first preferredembodiment of the present invention;

FIG. 8B is a sectional view taken along line VIIIb–VIIIb′ of FIG. 8A;

FIG. 9B is a sectional view taken along line IXb–IXb′ of FIG. 9A, and itshows a step following that depicted in FIG. 8B;

FIG. 10B is a sectional view taken along line Xb–Xb′ of FIG. 10A, andshows a step following that depicted in FIG. 9B;

FIG. 11B is a sectional view taken along line XIb–XIb′ of FIG. 11A, andshows a step following that depicted in FIG. 10B;

FIG. 12 is a schematic view of a thin film transistor substrate for aliquid crystal display according to a fourth preferred embodiment of thepresent invention;

FIGS. 13 and 14 are sectional views taken along lines XIII–XIII′ andXIV–XIV′, respectively, of FIG. 12;

FIG. 15A is a schematic view of a first step in the manufacture of athin film transistor substrate according to a fourth preferredembodiment of the present invention;

FIGS. 15B and 15C are sectional views taken along lines XVb–XVb′ andXVc–XVc′, respectively, of FIG. 15A;

FIGS. 16A and 16B are sectional views taken along lines XVb–XVb′ andXVc–XVc′, respectively, of FIG. 15A, and they show steps following thosedepicted in FIGS. 15B and 15C, respectively;

FIG. 17A is a schematic view of a thin film transistor substrate in amanufacturing step following that depicted in FIGS. 16A and 16B;

FIGS. 17B and 17C are sectional views taken along lines XVIIb–XVIIb′ andXVIIc–XVIIc′, respectively, of FIG. 17A;

FIGS. 18A, 19A and 20A are sectional views taken along line XVIIb–XVIIb′of FIG. 17A for showing sequential steps in the manufacturing processfollowing the step illustrated in FIG. 17B;

FIGS. 18B, 19B and 20B are sectional views taken along line XVIIc–XVIIc′of FIG. 17A for showing sequential steps in the manufacturing processfollowing the step illustrated in FIG. 17C;

FIG. 21A is a schematic view of a thin film transistor substrate in amanufacturing step following that depicted in FIGS. 20A and 20B;

FIGS. 21B and 21C are sectional views taken along line XXIb–XXIb′ andXXIc–XXIc′, respectively, of FIG. 21A;

FIG. 22 is a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a fifth preferredembodiment of the present invention; and

FIG. 23 is a sectional view taken along line XXIII–XIII′ of FIG. 22.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

In the preferred embodiments of the present invention, in order todetermine whether a completed thin film transistor (TFT) substrate isdefective, a probe pin is contacted to gate pads of gate wiring or datapads of data wiring. Since the number of data wires and data pads fortransmitting image signals increases as the resolution of an LCDincreases, misalignment between the pads and probe pin frequentlyoccurs. This increases contact resistance between the pads and probepin, making it difficult to perform the test defects of the TFTsubstrate. To solve this problem, the present invention uses a probe pinhaving a tip (contact portion) that is rounded, and a radius of therounded tip is 2 μm or less. This will be described in more detailbelow.

FIG. 1 shows a schematic view for describing a step in inspecting a thinfilm transistor array substrate for a liquid crystal display accordingto a preferred embodiment of the present invention.

In a completed TFT substrate, typically a gate insulation layer 30 isformed on an insulation substrate 10, and a data pad 68 (only a singledata pad 68 is shown in the partial view of FIG. 1) is provided on thegate insulation layer 30, the data pad 68 being connected to a data wire(not shown). Formed over the data pad 68 is a protection layer 70, and acontact hole 78 is formed in the protection layer 70 to expose the datapad 68. An auxiliary data pad 88 made of, for example, an IZO layer isformed over the contact hole 78 and partially overlaps the protectionlayer 70. As a result, the auxiliary data pad 88 contacts the data pad68 via the contact hole 78.

To determine if the TFT substrate is defective, a probe pin 200 of aninspection system is contacted to the auxiliary data pad 88. If duringthis process misalignment occurs between the probe pin 200 and theauxiliary data pad 88, a contact tip 220 of the probe pin 200nevertheless comes to contact the auxiliary data pad 88 as a result of astepped portion formed by the contact hole 78 of the protection layer70. However, a contact resistance between the auxiliary data pad 88 andthe contact tip 220 increases. If the contact tip 220 of the probe pin200 is provided in a curved shape with a radius of the curve at 2 μm orless, the contact tip 220 of the probe pin 200 contacts an outer surfaceof the auxiliary data pad 88, which is in direct contact with the datapad 68, in such a manner as to minimize the contact resistance betweenthe contact tip 220 and the auxiliary data pad 88. As a result, a moreprecise determination of the defectiveness of the TFT substrate isrealized. To further reduce contact resistance between the contact tip220 and the auxiliary data pad 88, it is possible to coat the contacttip 220 with gold (Au) or other such materials that have a lowresistance.

As examples of alternative methods, it is possible to (a) form a padportion, which includes the data pad, in a convex shape; (b) form a padauxiliary layer on a layer identical to a semiconductor layer at acenter portion of the data pad in order to increase an area that theprobe pin contacts; or (c) remove the insulation layer on the padportion such that the data pad is exposed. Further, a pad auxiliarylayer may be inserted under the data pad of a low-resistance aluminumgroup material, after which the pad auxiliary layer is connected to anIZO auxiliary pad.

FIG. 2 shows a schematic view of a thin film transistor substrate for aliquid crystal display according to a first preferred embodiment of thepresent invention, and FIG. 3 shows a sectional view taken along lineIII–III′ of FIG. 2. The drawings show only a section of the substrate.It is to be assumed that many of the elements described are formed aplurality of times over the substrate.

Gate wiring is formed on an insulation substrate. The gate wiring ismade of an aluminum group metal having a low resistance. The gate wiringincludes gate lines 22 formed horizontally (in FIG. 2) and gate pads 24connected to ends of the gate lines 22. The gate pads 24 receive gatesignals and transmit the gate signals to the gate lines 22 The gatewiring also includes and gate electrodes 26 of thin film transistors.The gate electrodes 26 is connected to the gate lines 22.

A gate insulating layer 30 covers the gate wiring. The gate insulatinglayer 30 is made of a material such as SiN_(x). A semiconductor layer 40is formed over the gate insulating layer 30 at areas corresponding toand in the vicinity of the gate electrodes 26. The semiconductor layer40 is made of a semiconductor material such as amorphous silicon. Ohmiccontact layers 55 and 56 are formed over the semiconductor layer 40. Theohmic contact layers 55 and 56 are made of a material such as n+amorphous silicon hydride, which is doped with n-type impurities at ahigh concentration. Further, a pad auxiliary layer 45, comprised ofamorphous silicon layers 44 and 54, is formed at predetermined locationsover that gate insulation layer 30. The pad auxiliary layer 45 is madeon the same layer as the semiconductor layer 40 or the ohmic contactlayers 55 and 56.

Data wiring is formed over the gate insulation layer 30 and the ohmiccontact layers 55 and 56. The data wiring is made of a metal such asmolybdenum (Mo) or a molybdenum-tungsten (MoW) alloy, chrome (Cr),tantulum (Ta), and titanium (Ti). The data wiring includes data lines 62formed vertically (in FIG. 2) intersecting the gate lines 22 to therebydefine pixels and source electrodes 65 branched from the data lines 62and extending to cover the ohmic contact layer 55. The data wiringincludes drain electrodes 66 separated from the source electrodes 65 andformed over the ohmic contact layer 56 on a side opposite the sourceelectrodes 65 with respect to the gate electrodes 26. Also included inthe data wiring are data pads 68 connected to one end of the data lines62 and formed covering the pad auxiliary layer 45, the data pads 68receiving image signals.

In the case where the elements 62, 65, 66 and 68 of the data wiring areformed in two or more layers, it is preferable that one layer is formedof a conducting material such as a low resistance aluminum groupmaterial, and another layer is made of a material that has good contactproperties with the first material, for example, Cr/Al (or an aluminumalloy) or Al/Mo, etc.

A protection layer 70, which is made of SiN_(x), is formed over the datawiring and over portions of the semiconductor layer 40 not covering thedata wiring. Contact holes 76 and 78 respectively exposing the drainelectrodes 66 and the data pads 68, and a contact hole 74 exposing thegate insulation layer 30 and the gate pads 24 are formed in theprotection layer 70. The contact holes 74 and 78 that expose the gatepads 24 and the data pads 68, respectively, can be formed having anglesor in a circular shape, and have an area that does not exceed 2 mm×60 μmbut preferably at least 0.5 mm×15 μm. Further, the contact hole 78 ispreferably larger than the pad auxiliary layer 45.

Pixel electrodes 82 are formed on the protection layer 70 and areelectrically connected to the drain electrodes 66 via the contact hole76. Further, auxiliary gate pads 86 and auxiliary data pads 88respectively connecting the gate pads 24 via that contact holes 74 andthe data pads 68 via the contact holes 78 are formed on the protectionlayer 70. The pixel electrodes 82 and the auxiliary gate and data pads86 and 88 are made of IZO (indium zinc oxide). With the formation of thepad auxiliary layer 45 under the data pads 68, the auxiliary data pads88 are substantially flat. Accordingly, no stepped region is formed bythe protection layer 70 such that the area of contact between thecontact tip 220 of the probe pin 200 (see FIG. 1) and the auxiliary datapad 88 is increased. Therefore, contact resistance between the auxiliarypads 88 and the contact tip 220 of the probe pin 200 is minimized duringtesting of the substrate.

The TFT array substrate of the first embodiment of the present inventionhas a contact structure between the gate pads 24, which are made of analuminum group metal, and the auxiliary gate pads 86, which are made ofIZO. The contact resistance of this contact structure is 10% or lesswith respect to the elements 22, 24 and 26 of the gate wiring, and ispreferably at or less than 0.15 Ω·cm². In a 14.1-inch liquid crystalpanel, a contact resistance of the pad portions is within the range of0.05˜0.1 Ω·cm².

The pixel electrodes 82, with reference to FIGS. 1 and 2, overlap thegate lines 22 to form a storage capacitor. When a storage capacitance isinsufficient, a storage capacitance wiring can be added to the samelayer as the elements 22, 24 and 26 of the gate wiring. Further, thepixel electrodes 82, auxiliary gate pads 86, and auxiliary data pads 88may be formed before the protection layer 70, and may also be formedbefore the elements 62, 65, 66 and 68 of the data wiring.

With the structure as described above, the elements 22, 24 and 26 of thegate wiring are made of a low-resistance aluminum group material suchthat it can be applied to a large-screen, high resolution LCD. Also,this enables the contact resistance of the pad portions to be minimizedand prevents corrosion.

In addition, with the formation of the pad auxiliary layer 45, theauxiliary data pads 88 are formed in a flat or protruded shape such thatthe area of contact for the probe pin 200 is increased, therebypreventing contact defects and limiting the contact resistance betweenthe probe pin 200 and the auxiliary data pads 88 during panel testing inthe LCD manufacturing process. The pad auxiliary layer 45 may be formedon the same layer as the elements 22, 24 and 26 of the gate wiring.

As a method of forming the pad portions in a protruded shape, the gateinsulation layer 30 and the protection layer 70 of the pad portions,where the data pads 68 are provided, are removed. This will be describedin more detail with reference to the drawings. With the exception of thepad portions, the structure to be described is identical to that of thefirst preferred embodiment of the present invention. Accordingly, likereference numerals will be used for like elements and a detaileddescription of identical elements will not be provided.

FIG. 4 shows a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a second preferredembodiment of the present invention, and FIG. 5 shows a sectional viewtaken along line V–V′ of FIG. 4.

The gate insulation layer 30 and the protection layer 70 are removedfrom a specific portion P of the pad portions where the data pads 68 areformed, except for an area under the data pads 68 where the gateinsulation layer 30 is left remaining. The auxiliary data pads 88 fullycover the data pads 68 and extend a predetermined distance over thesubstrate 10. As a result, the auxiliary data pads 88 are formed in aprotruding manner. The same effects as with the first embodiment areachieved with this structure.

In another structure, a low-resistance pad auxiliary layer may beprovided on the same layer as the elements 22, 24 and 26 of the gatewiring as described above. With the exception of the pad portions, thisstructure, which will be described below, is identical to that of thefirst preferred embodiment of the present invention. Accordingly, likereference numerals will be used for like elements and a detaileddescription of identical elements will not be provided.

FIG. 6 shows a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a third preferredembodiment of the present invention, FIG. 7 shows a sectional view takenalong line VII–VII′ of FIG. 6.

Pad auxiliary layers 25, which are made of an aluminum group conductingmaterial, are formed on the same layer as the elements 22, 24 and 26 ofthe gate wiring. The data pads 68 are formed over the gate insulationlayer 30, which covers the pad auxiliary layers 25. Contact holes 69 areformed in the data pads 68 and the gate insulation layer 30 such thatthe pad auxiliary layers 25 are exposed. The contact holes 69 may becylindrical or rectangular, and may be formed having a plurality of rowsand columns. The data pads 68 are partially covered by the protectionlayer 70. That is, contact holes 78 formed in the protection layer 70are larger than the contact holes 69 of the data pads 68 such that thedata pads 68 are only partially covered by the protection layer 70.

The auxiliary data pads 88 are formed covering the above structure suchthat the auxiliary data pads 88 contact the data pads 68 and the padauxiliary layers 25. As a result, a pad portion structure with a lowcontact resistance is achieved to minimize the contact resistance withthe probe pin.

A method for manufacturing the TFT substrate for an LCD according tofirst preferred embodiment of the present invention will now bedescribed with reference to FIGS. 2 and 3, and FIGS. 8A through 11B.Manufacturing methods of the TFT substrate according to the second andthird preferred embodiments of the present invention will also bedescribed.

With reference first to FIGS. 8A and 8B, a layer of a low-resistancealuminum group metal is formed on the substrate 10 to a thickness ofapproximately 2,500 Å. This layer is then patterned to form the gatewiring, which includes the gate lines 22, gate electrodes 26 and thegate pads 24. For the third embodiment, the pad auxiliary layer 25 isformed together with the gate wiring to realize the data pad portions.

Next, with reference to FIGS. 9A and 9B, three layers are formed on thesubstrate 10 over the gate wiring. The three layers include a SiN_(x)layer, an amorphous silicon layer, and a doped amorphous silicon layer.A mask is then used to pattern the layers into the gate insulation layer30, the semiconductor layer 40 and a doped amorphous silicon layer 50.The pad auxiliary layer 45, which includes the amorphous silicon layers44 and 54, is also formed in this process.

It is preferable that the gate insulation layer 30 is deposited over aninterval of 5 minutes or more at a temperature of at least 300° C. Whenforming the gate insulation layer 30, the gate insulation layer 30 isprovided over the gate wiring, then a portion or all of an AlO_(x) layerhaving a high resistance may be removed and a low-resistance reactionlayer, which is extracted from the aluminum group metal layer, may beformed. Further, before depositing the gate insulation layer 30, inorder to prevent the formation of an AlO_(x) layer on the aluminum groupmetal layer (i.e., the elements 22, 24 and 26 of the gate wiring), it ispreferable that a rinsing process using plasma containing oxygen, heliumor argon be performed in situ.

Following the above processes, with reference to FIGS. 10A and 10B, ametal layer made of chrome, molybdenum, a molybdenum alloy, titanium,tantalum, etc. is formed, then a photolithography process using a maskis performed to form the data wiring. In particular, formed in thisprocess are the data lines 62 that cross the gate lines 22, the sourceelectrodes 65 connected to the data lines 62 and extending over the gateelectrodes 26, the data pads 68 connected to one end of the data lines62 and covering the pad auxiliary layer 45, and drain electrodes 66separated from the source electrodes 65 and located opposite around thegate electrodes 26. To realize the structure of the third preferredembodiment, the data pads 68 are formed having contact holes 69 over thepad auxiliary layer 25 (see FIGS. 6 and 7).

Subsequently, the doped amorphous silicon layer 50 not covering theelements 62, 65, 66 and 68 of the data wiring is etched to be dividedinto two portions about the gate electrodes and to expose thesemiconductor pattern 40 between the amorphous silicon layer 40. It ispreferable to then perform an oxygen plasma process to stabilize asurface of the amorphous silicon layer 40.

After the above processes, with reference to FIGS. 11A and 11B, aninorganic insulation layer is deposited to form the protection layer 70.At this time, as with the gate insulation layer 30, it is preferablethat the protection layer 70 is deposited over an interval of 5 minutesor more at a temperature of at least 300° C. Also, a low-resistancereaction layer may be formed on the surface of the aluminum group metallayer (i.e., 22, 24 and 26), and a high-resistance metal oxide layerformed during manufacture may be partly or completely removed. Ofcourse, the same effects can be obtained also in the case where theelements 62, 65, 66 and 68 of the data wiring contain aluminum groupmetals.

Next, patterning is performed through a photolithography process using amask to thereby form the contact holes 74, 76 and 78 for exposing thegate pads 24, the drain electrodes 66 and the data pads 68,respectively. The contact holes 74, 76 and 78 can be formed in acylindrical or rectangular shape. Also, the contact holes 74 and 78exposing the pads 24 and 68, respectively, preferably do not exceed anarea of 2 mm×60 μm and are greater than an area of 0.5 mm×15 μm.

To realize the structure of the second preferred embodiment, theprotection layer 70 and the gate insulation layer 30 are removed fromthe data pad portions. For the third preferred embodiment, the gateinsulation layer 30 exposed through the contact holes 69 of the datapads 68 is removed when forming the contact holes 78 of the protectionlayer 70, and the pad auxiliary layer 25 is exposed through the contactholes 69 of the data pads 68.

Lastly, with reference to FIGS. 2–8, an IZO layer is deposited, andpatterned using a mask to form the pixel electrodes 82, which areconnected to the drain electrodes 66 through the contact holes 76, andto form the auxiliary gate pads 86 and the auxiliary data pads 88, whichare respectively connected to the gate pads 24 through the contact holes74 and to the data pads 68 through the contact holes 78. It is possibleto perform a pre-heating process before depositing the IZO layer, and itis preferable that nitrogen gas is used in order to prevent theformation of a metal oxide layer on the metal layer (i.e., the elements22, 66 and 68) exposed by the contact holes 74, 76 and 78.

In the preferred embodiments of the present invention, in order tominimize the contact resistance of the contact portions, it ispreferable that the IZO is deposited in the range of between roomtemperature and 200° C. Also, to form the IZO thin film, IDIXO (indiumx-metal oxide) of Idemitsu Company was used in the present invention, inwhich preferably there are In₂O₃ and ZnO containing 15–20 at % of Zntherein. Before depositing the IZO, to prevent the formation of AlO_(x)on the aluminum group metal layer 22, 24, and 26 of the gate wiring, arinsing process using plasma containing oxygen, helium or argon may beperformed in situ, and a rinsing process using an aluminum etchingsolution may be performed for patterning the aluminum group metal layer.At this time, it is preferable that the aluminum etching solutioncontains nitric acid (HNO₃), hydrochloric acid (HPO₄), acetic acid(CH₃COOH) and deionized water, and the rinsing process using the etchingsolution is performed for 10 seconds or less, and more preferably in therange of 7–10 seconds.

In the manufacturing method of the present invention as described above,an annealing process is performed when depositing the insulation layers30 and 70 and before depositing the IZO layer in order to improve thecontact characteristics between the IZO and aluminum group metal.Accordingly, the contact resistance of the contact portions is minimizedsuch that the reliability of the contact portions is ensured.

Also, as described above, the data pad portions are formed in aprotruding shape, or auxiliary pads and a low-resistance auxiliary layerare additionally provided to minimize the contact resistance of the padportions and such that the contact reliability of the pad portions isimproved during inspection, which takes place in the manufacturingprocess.

In the manufacturing method as described above, five masks are used.However, it is also possible to use only four masks. This will bedescribed in more detail with reference to the drawings.

FIG. 12 shows a schematic view of a thin film transistor substrate for aliquid crystal display according to a fourth preferred embodiment of thepresent invention, and FIGS. 13 and 14 show sectional views taken alonglines XIII–XIII′ and XIV–XIV′, respectively, of FIG. 12.

Gate wiring including gate lines 22, gate pads 24 and gate electrodes26, which are made of an aluminum group metal, are formed on aninsulation substrate 10. The gate wiring also includes storageelectrodes 28 provided in parallel to the gate lines 22 on the substrate10 and which receive voltages such as a common electrode voltage inputto common electrodes. The storage electrodes 28 are overlapped by aconducting pattern 64, which is used as a storage capacitor and isconnected to pixel electrodes 82 (to be described hereinafter), tothereby form a storage capacitor for improving a potential maintenancecapacity of the pixels. If a storage capacity generated by theoverlapping of the pixel electrodes 82 and the gate lines 22 issufficient, it is possible to omit the storage electrodes 28. Further, apad auxiliary layer 25 is formed on the substrate 10 as in the thirdembodiment.

A gate insulation layer 30 made of, for example, SiN_(x) is formed overthe elements 22, 24, 26 and 28 of the gate wiring and the pad auxiliarylayer 25. Formed over the gate insulation layer 30 are semiconductorpatterns 42 and 48, which are made of a semiconductor such ashydrogenated amorphous silicon. Ohmic contact layer patterns (orintermediate patterns) 55, 56 and 58 are formed over the semiconductorpatterns 42 and 48. The ohmic contact layer patterns 55, 56 and 58 aremade of amorphous silicon that is doped at a high concentration withn-type impurities such as phosphorus (P).

Data wiring is formed over the ohmic contact layer patterns 55, 56 and58. The data wiring is made of metal such as chrome, molybdenum, amolybdenum alloy, tantalum, or titanium. The data wiring includes (a) adata line portion having data lines 62 formed vertically (in FIG. 12),data pads 68 connected to one end of the data lines 62 and receivingimage signals, and source electrodes 65 of a thin film transistor whichare branched from the data lines 62; (b) drain electrodes 66 of a thinfilm transistor separated from the elements 62, 68 and 65 of the dataline portion, and positioned opposite the source electrodes 65 withrespect to the gate electrodes 26 or a thin film transistor channel C;and (c) a storage capacitor conducting pattern 64 positioned over thestorage electrodes 28. In the case where the storage electrodes 28 arenot formed, the storage capacitor conducting pattern 64 is not required.The data pads 68 and the layers 42 and 55 under the data pads 68 arealigned, and include a contact hole 69 exposing the pad auxiliary layer25.

The elements 62, 64, 65, 66 and 68 of the data wiring can be realizedthrough a double layer structure that includes two conducting layers: aconducting layer made of molybdenum, a molybdenum alloy, tantalum, ortitanium; and a conducting layer made of an aluminum group metal.

The ohmic contact layer patterns 55, 56 and 58 reduce the contactresistance of the semiconductor patterns 42 and 48, which are formedunder the ohmic contact layer patterns 55, 56 and 58. They also reducethe contact resistance of the elements 62, 64, 65, 66 and 68 of the datawiring, which are formed over the ohmic contact layer patterns 55, 56and 58. The ohmic contact layer patterns 55, 56 and 58 are formed in ashape identical to the elements 62, 64, 65, 66 and 68 of the datawiring. In particular, the ohmic contact layer pattern 55 is formedidentically to the elements 62, 65 and 68, the ohmic contact layerpattern 56 is formed identically to the drain electrodes 66, and theohmic contact layer pattern 58 is formed identically to the storagecapacitor conducting pattern 64.

The semiconductor patterns 42 and 48, if the channel C is ignored, areformed in substantially the same shape as the elements 62, 64, 65, 66and 68 of the data wiring and the ohmic contact layer patterns 55, 56and 58. In particular, the storage capacitor semiconductor pattern 48,the storage capacitor conducting pattern 64 and the ohmic contact layerpattern 58 are formed in the same shape. However, the thin filmtransistor semiconductor pattern 42 is formed slightly different fromthe data wiring and the ohmic contact layer patterns 55 and 56. That is,while the source electrodes 65, the drain electrodes 66, and the ohmiccontact layer patterns 55 and 56 are separated at the channel C, thesemiconductor pattern 42 is not separated at this area and continuesthrough the channel C.

A protection layer 70 is formed over the elements 62, 64, 65, 66 and 68of the data wiring. The protection layer 70 is made of SiNi_(x). Theprotection layer 70 includes contact holes 76, 78 and 72 for exposingthe drain electrodes 66, the storage capacitance conducting pattern 64and the data pads 68, respectively. The protection layer 70 alsoincludes a contact hole 74 for exposing the gate insulation layer 30. Itis preferable that the contact hole 78 of the protection layer 70 islarger than the pad auxiliary layer 25.

The pixel electrodes 82 are formed over the protection layer 70, andreceive image signals from the thin film transistor and generate anelectric field together with an electrode formed on an upper substrate.The pixel electrodes 82 are made of a transparent conducting materialsuch as IZO, and are physically and electrically connected to the drainelectrodes 66 through the contact hole 76 to receive the image signals.Further, the pixel electrodes 82 overlap the gate lines 22 and the datalines 62 to increase an aperture ratio. However, there may be nooverlapping of these elements. The pixel electrodes 82 are alsoconnected to the storage capacitance conducting pattern 64 through thecontact hole 72 to receive image signals from the storage capacitanceconducting pattern 64.

The auxiliary gate pads 86 and the auxiliary data pads 88 are formedrespectively over the gate pads 24 and the data pads 68 to make contactwith the same through the contact holes 74 and 78. As a result, contactbetween the pads 24 and 68 and an external circuit unit is ensured, andthe pads 24 and 68 are protected. However, such a structure is optional.The auxiliary data pads 88 are physically and electrically connected tothe pad auxiliary-layer 25 via the contact hole 69 of the data pads 68.

A method for manufacturing the TFT substrate for liquid crystal displaysof FIGS. 12, 13 and 14 using four masks will now be described.

With reference first to FIGS. 15A, 15B and 15C, an aluminum group metallayer is deposited on the substrate, then a photolithography processusing a mask is performed to form the gate wiring, which includes thegate lines 22, the gate pads 24, the gate electrodes 26, and the storageelectrodes 28, and to form the pad auxiliary layer 25.

Next, with reference to FIGS. 16A and 16B, the gate insulation layer 30,the semiconductor layer 40 and the doped amorphous silicon layer 50,which are made of SiNi_(x), are deposited using a chemical vapordeposition method respectively at thicknesses of 1,500 to 5,000 Å, 500to 2,000 Å, and 300 to 600 Å. Subsequently, a conducting layer 60, whichincludes a metal layer of chrome, is deposited at a thickness of 1,500to 3,000 Å using a sputtering process, for example, after which aphotosensitive layer 110 is deposited at a thickness of between 1 μm and2 μm. It is preferable that the gate insulation layer 30 is depositedover an interval of 5 minutes or more at a temperature of at least 300°C. When forming the gate insulation layer 30, the gate insulation layer30 is provided over the gate wiring, then a portion or all of an AlO_(x)layer having a high resistance may be removed, and a low-resistancereaction layer, which is extracted from the aluminum group metal layer,may be formed. Further, before depositing the gate insulation layer 30,in order to prevent the formation of an AlO_(x) layer on the aluminumgroup metal layer (i.e., the elements 22, 24 and 26 of the gate wiring),it is preferable that a rinsing process using plasma containing oxygen,helium or argon be performed in situ.

Then, light is irradiated on the photosensitive layer 110 using a maskto develop the photosensitive layer 110, and, with reference to FIGS.17B and 17C, photosensitive layer patterns 112 and 114 are formed. Here,the channel C of the thin film transistor, that is, the photosensitivelayer pattern 114 between the source electrodes 65 and the drainelectrodes 66 is thinner than the photosensitive layer pattern 112,which is positioned at a data wiring portion A, or areas where theelements 62, 64, 65, 66 and 68 of the data wiring are formed. Thephotosensitive layer at remaining portions is removed. At this time, aratio in the thicknesses of the photosensitive layer patterns 112 and114 varies depending upon conditions of the etching process. Preferably,the ratio between the thickness of the photosensitive layer pattern 114to the thickness of the photosensitive layer pattern 112 is 1:2 or less.

There are various methods that can be used to adjust the thickness ofthe photosensitive layer patterns 112 and 114. For example, slits orlattice shapes can be used to control the amount of irradiated light, ora semitransparent layer can be used. In the case where slits are used,it is preferable that a pattern line width between the slits or aninterval between the patterns, that is, a width of the slits, is smallerthan a resolution of an exposure device. If a semitransparent layer isused to control the transmissivity when manufacturing the mask, thinfilms of differing transmissivity or different thicknesses may be used.

With the irradiation of light on the photosensitive layer through amask, portions directly exposed are fully dissolved, and areas where aslit pattern or a semitransparent layer is formed receive limited lightsuch that the high polymers are not completely dissolved. Also, in areaswhere a light-blocking layer are formed, the high polymers undergoalmost no dissolution. As the photosensitive layer is developed, onlyareas where the high polymers are not dissolved remain, and center areaswhere a limited amount of light is irradiated can be formed at a smallerthickness than where light is fully blocked. However, the exposing timemust be controlled since all the polymers dissolve if an excessivelyexposed to light.

The thin photosensitive layer pattern 114 is made of a photosensitivelayer that enables reflow, and is exposed using a mask with portionsthat fully allow the transmission of light and portions that fully blockthe transmission of light. Next, reflow is performed so that a portionof the photosensitive layer is flowed to areas where no photosensitivelayer remains. Next, the photosensitive layer 114 and layers under thesame, that is, the conducting layer 60, the doped amorphous siliconlayer 50 and the semiconductor layer 40 are etched. At this time, datawiring and the layers under the data wiring are left as is at the datawiring portion A, and only the semiconductor layers are left in thechannel C. At the remaining portions B, all three layers 40, 50 and 60are completely removed, and the gate insulation layer 30 is exposed.

With reference to FIGS. 18A and 18B, the conductive layer 60 exposed atthe portions B is removed such that the doped amorphous silicon layer 50is exposed. The contact holes 69 are also formed at this time. In thisprocess, either the dry etch or wet etch method may be used. Also, it ispreferable that the conducting layer 60 is etched, while thephotosensitive layer patterns 112 and 114 undergo almost no etching.However, when the dry etch method is used, since it is difficult to onlyetch the conducting layer 60 and not the photosensitive layer patterns,the photosensitive layer patterns 112 and 114 are also etched. In thiscase, the photosensitive layer pattern 114 is made thicker than in thewet etch method so that when the pattern 114 is removed, the conductinglayer 60 underneath is not exposed.

If the conducting layer 60 is Mo, a MoW alloy, Al, an Al alloy, or Ta,either the dry etch or wet etch method may be used. However, if theconducting layer 60 is made of Cr, it is preferable that the wet etchmethod be used since removal of Cr is difficult using the dry etchmethod. If the conducting layer 60 is made of Cr and the wet etch methodis used, CeNHO₃ may be used as the etching solution. If the conductinglayer 60 is made of Mo or MoW and the dry etch method is used, a gasmixture of CF₄ and HCl or CF₄ and O₂ may be used, with the etching ratioof the photosensitive layer being almost identical in the latter case.

Accordingly, with reference to FIGS. 18A and 18B, the only areas leftremaining are the channel C and the conducting layer of the data wiringportion B, that is, the source/drain conducting pattern 67 and thestorage capacitor conducting pattern 64, whereas the conducting layer 60of the remaining portion B is completely removed such that the dopedamorphous silicon layer 50 is exposed. At this time, the remainingconducting patterns 67 and 64, except where the source and drainelectrodes 65 and 66 are connected, are patterned identically to theelements 62, 64, 65, 66 and 68 of the data wiring. Further, when the dryetch method is used, the photosensitive layer patterns 112 and 114 areetched to a predetermined thickness.

Next, with reference to FIGS. 19A and 19B, the remaining portions B andthe doped amorphous silicon layer 50 and semiconductor layer 40 exposedthrough the contact hole 69 are removed together with the photosensitivelayer pattern 114 using a dry etching process. At this time, etchingmust be performed such that the photosensitive layer patterns 112 and114, the doped amorphous silicon layer 50 and the semiconductor layer 40(the semiconductor layer 40 and the doped amorphous silicon layer 50have almost no etch selectivity) are etched simultaneously, while thegate insulation layer 30 is not etched. In particular, it is preferablethat etch ratios of the photosensitive layer patterns 112 and 114, andthe semiconductor layer 40 are almost identical. Nearly identicalthicknesses can be obtained if, for example, a mixture of SF₆ and HCl,or of SF₆ and O₂ is used. If the etch ratios of the photosensitive layerpatterns 112 and 114, and the semiconductor layer 40 are identical, itis necessary that a thickness of the photosensitive layer pattern 114 isequal to or less than the added thicknesses of the semiconductor layer40 and the doped amorphous silicon layer 50.

As a result of the above, the photosensitive layer pattern 114 of thechannel C is removed such that the source/drain conducting pattern 67 isexposed, and the remaining portions B and the doped amorphous siliconlayer 50 of the contact hole 60 and the semiconductor layer 40 areremoved so that the gate insulation layer 30 is exposed. Since thephotosensitive layer pattern 112 of the data wiring portion A is alsoetched, the thickness thereof is reduced. The semiconductor patterns 42and 48 are completed in this step. Reference numerals 57 and 58 indicatean intermediate layer pattern of the source/drain conducting pattern 67and an intermediate layer pattern of the storage capacitor conductingpattern 64. Photosensitive residue remaining on a surface of thesource/drain conducting pattern 67 of the channel C is removed throughan ashing process.

Thereafter, with reference to FIGS. 20A and 20B, the source/drainconducting pattern 67 and the source/drain intermediate layer pattern 57are etched to remove the same. At this time, it is possible to perform adry etch process to both the source/drain conducting pattern 67 and theintermediate layer pattern 57, or to perform wet etching for thesource/drain conducting pattern 67 and dry etching for the intermediatelayer pattern 57. In the case where dry etching is performed for bothelements 67 and 57, it is preferable that an etch selection ratio of thesource/drain conducting pattern 67 and the intermediate layer pattern 57is large. If the etch selection ratio is not large, an etch completionpoint is not easily found such that it becomes difficult to control thethickness of the semiconductor pattern 42 remaining in the channel C.For example, the source/drain conducting pattern 67 may be etched usinga mixture of SF₆ and O₂. In the case where both the wet etch and dryetch methods are used, although a side surface of the source/drainconducting pattern 67 is etched during wet etching, the intermediatelayer pattern 57 undergoes almost no etching during the dry etchprocess. Accordingly, a stepped pattern results.

A mixture of CF₄ and HCl, or of CF₄ and O₂ may be used for the etchingprocess. If the mixture of CF₄ and HCl is used, the semiconductorpattern 42 is left at a uniform thickness. At this time, with referenceto FIG. 20B, a portion of the semiconductor pattern 42 may be removed,and the photosensitive layer pattern 112 may also undergo etching to apredetermined thickness. Etching at this point must be performed in sucha manner that the gate insulation 30 is not etched. Also, it ispreferable that the photosensitive material is such that the elements62, 64, 65, 66 and 68 of the data wiring are not exposed when thephotosensitive layer pattern 112 is etched.

As a result of the above process, the source electrodes 65 and the drainelectrodes 66 are separated, and the elements 62, 64, 65, 66 and 68 ofthe data wiring and the contact layer patterns 55, 56 and 58 arecompleted. Lastly, the photosensitive layer pattern 112 remaining in thedata wiring portion A is removed. The photosensitive layer pattern 112may also be removed after the removal of the source/drain conductingpattern 67 of the channel C and before the removal of the intermediatelayer pattern 57.

As described above, both wet etching and dry etching or only a dry etchprocess may be performed. In the latter case, although the process issimplified since only a single type of etching is performed, it may bedifficult to satisfy all etch conditions. On the other hand, if bothtypes of etching processes are used, etch conditions are satisfied butthe etch process becomes more complicated.

With reference to FIGS. 21A and 21C, after forming the elements 62, 64,65, 66 and 68 of the data wiring, SiNi_(x) is deposited through a CVDprocess to form the protection layer 70. Next, the protection layer 70and the gate insulation layer 30 are etched to form the contact holes76, 74, 78 and 72, which respectively expose the drain electrodes 66,the gate pads 24, the data pads 68 and the storage capacitor conductingpattern 64. Here, the gate insulation layer 30 exposed through thecontact hole 69 of the data pad 68 is also removed such that the padauxiliary layer 25, which is a low resistance aluminum group metal, isexposed through the contact holes 69 and 78. It is preferable that theprotection layer 70 is deposited over an interval of 5 minutes or moreat a temperature of at least 300° C. A portion or all of a highresistance metal oxide layer formed during the manufacturing process maybe removed. It is preferable that an area of the contact holes 74 and 78exposing the pads 24 and 68 does not exceed 2 mm×60 μm and is at least0.5 mm×15 μm.

Finally, with reference to FIGS. 12 through 14, an IZO layer isdeposited at a thickness of between 400 and 500 Å, and the layer isetched using a mask to form the pixel electrodes 82 connected to thedrain electrodes 66 and the storage capacitor conducting pattern 64, theauxiliary gate pads 86 connected to the gate pads 24, and the auxiliarydata pads 88 connected to the data pads 68 and the aluminum group padauxiliary layer 25. The etch solution used for patterning at this timeis a chrome etch solution, which is used for etching chrome metallayers. Chrome etch solutions do not corrode aluminum group metals andprevent the corrosion of aluminum group metals exposed in the contactstructure. An example of such an etch solution isHNO₃/(NH₄)₂Ce(NO₃)₆/H₂O. It is preferable that a pre-heating process beperformed before depositing the IZO layer. At this time, it ispreferable that nitrogen be used to prevent the formation of a metaloxide layer on the layers 24, 25, 64, 66 and 68. Further, to minimizethe contact resistance of the contact portions, it is preferable thatthe IZO layer be deposited in a temperature range of between roomtemperature and 200° C. Also, to form the IZO thin film, it ispreferable that In₂O₃ and ZnO containing 15–20 at % of Zn are containedtherein. Before depositing the IZO, to prevent the formation of AlO_(x)on the aluminum group metal layer 24, a rinsing process using plasmacontaining oxygen, helium or argon may be performed in situ.

In the fourth embodiment of the present invention, in addition to theeffects obtained in the first or third embodiments, the elements 62, 64,65, 66 and 68 of the data wiring, as well as the contact layer patterns55, 56 and 58 and the semiconductor patterns 42 and 48 are formed usinga single mask. Also, in this process, the source electrodes 65 and thedrain electrodes 66 are separated such that the manufacturing process issimplified.

In a manufacturing method for a thin film transistor substrate for LCDsin which four masks are used as in the first embodiment, the padauxiliary layer may be formed on the same layer as the gate wiring suchthat the data pad portions are formed substantially in a flat shape,thereby increasing the contact area of the probe pin at the data padportions. This will be described in more detail with reference to thedrawings. Here, the majority of the structure is identical to the fourthpreferred embodiment of the present invention. Accordingly, except forthe pad portions, the remainder of the structure will not be describedin detail and like reference numerals will be used for like elements.

FIG. 22 is a schematic view of a data pad in a thin film transistorsubstrate for a liquid crystal display according to a fifth preferredembodiment of the present invention; and FIG. 23 is a sectional viewtaken along line XXIII–XIII′ of FIG. 22.

As shown in the drawings, a gate insulation layer 30 is formed coveringa pad auxiliary layer 25. Formed in sequence over the gate insulationlayer 30 are a semiconductor pattern 42, an ohmic contact layer pattern55, and a data pad 68. Further, a protection layer 70 is formed over thegate insulation layer 30, and has a contact hole 78 that exposes thedata pad 68 and which is larger than the pad auxiliary layer 25. Theprotection layer 70 is made of SiNi_(x) or an organic insulationmaterial. An auxiliary data pad 88 made of a transparent conductingmaterial is formed over the protection layer 70.

In the fifth embodiment, as with the second embodiment, the padauxiliary layer 25 is provided under the data pad 68 to minimize thestepped formation of the protection layer 70. Accordingly, the auxiliarydata pad 88 is formed nearly level on the protection layer 70. As aresult of this structure, an area of the auxiliary data pad 88 contactedby the probe pin is increased such that a contact defect is prevented,and a contact resistance between these two elements is minimized.

In the present invention as described above, the pad portion contactedby the probe pin is either formed in a protruded shape, its areaincreased, or a low-resistance pad auxiliary layer added. As a result,when performing inspection of the LCD during the manufacturing process,contact defects of a probe pin and a contact resistance of the padportions are minimized. Further, the reliability of the contact portionsis ensured by limiting its contact resistance.

Although preferred embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

For example, although the structure of the data pad portions was changedin the above embodiments, it is also possible to vary the structure ofthe gate pad portions.

1. A substrate, comprising: a gate line comprising a gate electrode; agate insulation layer covering the gate line; a storage electrodedisconnected from the gate line; a semiconductor layer formed over thegate insulation layer; a data wire formed over the gate insulation layerand comprising a source electrodes; data wiring elements including aconducting pattern and a drain electrode overlapping the storageelectrode; a protection layer covering the data wiring elements andhaving a plurality of contact holes formed therethrough to the datawiring elements; and a pixel electrode connected to the data wiringelements through at least more than two of the contact holes.
 2. Thesubstrate of claim 1, the data line further comprising a drainelectrode.
 3. The substrate of claim 2, wherein the drain electrode isdisconnected from the conducting pattern.
 4. The substrate of claim 1,further comprising an auxiliary pad connected to at least one of thegate line and the data line.
 5. The substrate of claim 4, wherein theauxiliary pad is formed on the same layer as the pixel electrode.
 6. Thesubstrate of claim 1, further comprising an ohmic contact layer formedbetween the semiconductor layer and the data line.
 7. The substrate ofclaim 6, wherein the ohmic contact layer and the data line havesubstantially the same shape.
 8. The substrate of claim 7, wherein thesemiconductor layer has substantially the same shape with the data lineexcept for a portion overlying the gate electrode.